A vehicular antitheft device is disclosed in Patent Document 1, which is installed in a vehicle and configured to detect an abnormality of the vehicle caused by a theft action when the vehicle is subjected to theft and notify the detection to the outside.
Currently known antitheft systems generally include an incorporated antenna type in which a GPS (Global Positioning System) antenna is incorporated in an antitheft device, and a separated antenna type in which the GPS antenna is separated from the antitheft device. Parts disposed inside the antitheft device require high waterproofing performance due to the necessity of the protection against moisture and the like. The incorporated antenna type antitheft system is easy to improve the waterproof performance merely by covering the entire internal parts with a case.
On the other hand, in the separated antenna type antitheft system, the GPS antenna and the antitheft device are connected by the harness. A joint portion between the harness and the antitheft device unavoidably passes through the case and, hence, high waterproofing performance is required at a part of the joint portion passing through the case. To deal with this requirement, a grommet is provided on the case so that the harness passes through the grommet.
The grommet is a substantially cylindrical elastic member and used such that an outer peripheral surface of the cylindrical member is fitted with a through-hole of the case and an inner peripheral surface is fitted with the harness. When the harness is subjected to an external force tending to deflect the harness in a direction perpendicular to an axis of the harness, the grommet deforms in a radial direction to thereby allow displacement of the harness. However, when an amount of displacement of the harness exceeds a predetermined value, a gap is formed between the inner peripheral surface of the grommet and an outer peripheral surface of the grommet, allowing water to get into the case from the gap.
This means that the grommet merely provided to accommodate the passage of the harness will unavoidably cause reduction of the waterproofing performance due to a gap produced between the harness and the grommet when the harness is displaced. It is, therefore, desirable for the antitheft system of the type having a GPS antenna separated from an antitheft device to have enhanced waterproofing performance at a part of the case through which a wire extends.